Water Equivalent
It is the quantity of water whose thermal capacity is same as the heat capacity of the body . It is denoted by W .
W = ms = heat capacity of the body .
Latent Heat The heat energy absorbed or released at constant temperature per unit mass for change of state is called latent heat . Heat energy absorbed or released during change of state is given by
Q = mL where m = mass of the substance and L = latent heat . Its unit is cal / g or J / kg and its dimension is [ L 2 T -2 ].
For water at its normal boiling point or condensation temperature ( 100 ° C ), the latent heat of vaporisation is
L = 540 cal / g = 40.8 kJ / mol
= 2260 kJ / kg
For water at its normal freezing temperature or melting point ( 0 ° C ), the latent heat of fusion is
L = 80 cal / g = 60 kJ / mol = 336 kJ / kg
It is more painful to get burnt by steam rather than by boiling was 100 ° C gets converted to water at 100 ° C , then it gives out 536 heat . So , it is clear that steam at 100 ° C has more heat than wat 100 ° C ( i . e ., boiling of water ).
After snow falls , the temperature of the atmosphere becomes very This is because the snow absorbs the heat from the atmosphere to down . So , in the mountains , when snow falls , one does not feel too but when ice melts , he feels too cold .
There is more shivering effect of ice cream on teeth as compare that of water ( obtained from ice ). This is because when ice cream down , it absorbs large amount of heat from teeth .
Melting Conversion of solid into liquid state at constant temperature is melting .